Friday, March 29, 2013

One of the key issue of mobile phones, particularly smartphones, is that they are power hungry causing their battery doesn't last long. As a result, mobile power bank comes into the market as portable external power source to supplement the internal battery of the mobile phone or mobile device.

While most of the modern mobile devices nowadays are using Li-Polymer battery (鋰聚合物電池) as their power source, a lot of mobile power banks are using the cylindrical or prismatic Li-Ion battery (鋰離子電池).

The major problem or hazard of Li-Ion battery and Li-Polymer battery is that, they will overheat when charged for long time. There is an overcharge prevention IC on its circuit board to cut off the charging when the battery is fully charged. If the IC is malfunctioned, the battery might caught fire or explode when overcharged. (Note: the original article mentioned Li-Polymer will not explode due to overcharge, which I think is not true.)

Another disadvantage of Li-Ion battery is their lifespan will greatly reduced if they are operating in high temperature of 45°C and above. Li-Polymer battery, on the other hand, has higher endurance to high temperature, and can still operate over 4 hours in 85°C without much problem.

Nowadays, you can find a lot of power banks claimed to have charge capacity as high as 12000mAh, 18000mAh, 20000mAh, or even higher, selling at the Internet stores. If they are unbranded and selling at a very cheap price, you need to be alerted before placing your order.

The shorter power bank in the picture above consists of 4 Li-Ion 18650 batteries, while the longer one consists of 6 Li-Ion 18650 batteries. The size of the cylindrical Li-Ion battery in used is 18.25x65mm, and their manufacturing part number is normally in the form of XXX18650-XX.

The quality of Li-Ion battery differs.

Branded made-in-Japan (eg. Sanyo, Panasonic) one normally has capacity of at least 3100mAh, and comes with 1 year warranty. They have higher price too and won't be chosen to make the cheap power bank selling in the Internet stores.

Samsung OEM made-in-China Li-Ion battery has 4 grades. The highest A01 grade normally reserved for Samsung own use, while A02, A03 and A04 are made available for customers. Part number could be ICR18650-20, ICR18650-22, ICR18650-24, ICR18650-26, etc. If a power bank claimed to use Samsung batteries, the batteries inside are probably the A02~A04 type.

Certain unbranded made-in-china battery were found to have only 1600-1800mAh but also put in the 18650 code and claimed to have 3000mAh. The cheap power banks probably are using this kind of Li-Ion battery.

For the power bank with 12000mAh capacity above, its capacity is calculated like this:

3000mAh x 4 = 12000mAh

However, if the real capacity of the batteries inside is only 2200mAh, you can only get 2200mAh x 4 = 8800mAh.

For the power bank with 18000mAh capacity above, its capacity is calculated like this:

3000mAh x 6 = 18000mAh

However, if the real capacity of the batteries inside is only 2200mAh, you can only get 2200mAh x 6 = 13200mAh.

Beside the possible short-change in real capacity, since the size of the Li-Ion batteries are the same, some dishonest power bank might even use recycled batteries!

The picture above is said to be taken from a newly purchased cheap power bank, opened up for inspection. Note that the colour of the 6 Li-Ion batteries are all different, which is very unlikely if they are manufactured from the same batch.

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Also note that the soldering point is rusted and shows sign of multiple re-soldering. There is also leftover glue on the surface.

Worse still, what if the cheap dishonest power bank does not have a properly functioning overcharge / over-discharge circuit?

And even more ridiculous case, you probably get only a single Li-Ion battery with 2 bags of sand.

So, better be cautious when you buy power bank either from Internet or shop, especially when the product is unbranded and the price is cheap.

Note: The above article is excerpted and translated from its original source posted in Chinese by a Taiwanese called 曾家辉 in his Facebook page. The photos above are taken from his original article.

thanks for the review , i wanted to buy 10000 mah power bank for my nokia 808 pure 1400 mah phone , my doesnt last a single day on full charge , so can you suggesy which brand is better to buy , with compatibility and true promise

Those OEM mean fake or imitation, the most important in powerbank is the good design in PCB and use good branded cell like samsung ,sanyo or panasonic which is top brand in this field. those powerbank been produce by good PCB and branded cell sure can last must longer and perform much better compare to others.

The Chronovski iWallet Power bank 20K is probably the best sold on Qoo10 as it can charge the iPhone at least 6 times. If you get from other sellers, they will tell you their 20,000 mAh can charge 2 or 3 times only

Even the branded one can't be trusted. I bought the Mili King (18000mAh) which charged my 3000mAh batt for 3.5 times only (3000mAh x 3.5 = approx. 10500mAh only).A Metrans 10400mAh with built-in Qi wireless charging only last me for 2.5x on the same battery (3000mAh x 2.5 = approx. 7500mAh).Both power banks I returned to the seller and had my money refunded.

My yoobao transformers power bank just exploded. Bought in December 2013 @ low yat. It is simply too scary. Luckily, no one was injured. There was a loud sonic sound before it exploded. My curtains got burnt. No more powerbank for me.

I was really skeptical about buying Samurai Power Bank because i wasn’t sure if it was going to fill my battery as much as i'd like. Although, i am very happy with my purchase. My phone will be completely dead and it charges all the way to 100%. My sister uses my portable back up as well. It does charge a lot. I am very pleased!

Such a good and informative piece! I recently ended up with a charger that didn't work. Wish I'd read this beforehand. You can read about my experience here: http://techgirl.co.za/2014/06/30/not-all-portable-chargers-will-charge-your-phone/

Need help. What can you say about the brand bavin? And can you suggest at least 3 brands that I can check given the limited budget that I have? Say 40 dollars and eyeing for a 20000 mah or 15000 mah. Tia!

REAL CAPACITY CALCULATION FOR ALL POWERBANKS====================================Everyone complaining about low battery capacity please note there is loss of capacity as 3.7v 18650 [Li-ion] Batteries used in Powerbanks has to be stepped up to 5v output resulting in loss of Mah.[Capacity]

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It is the most reliable power bank brand in Singapore. I bought one when i was in Germany. And when i came back to Singapore, i bought two more from the Singapore agent. Really love a brand that has been around for more than 10 years.